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• Wing Kinematics: This is dependent on the wing structure and degrees of

freedom. In nature, the insect wing structure is membranous with veins running

longitudinally.

• Optimizing for Higher Lift: Both the lift and drag forces increase with frequency.

The maximum lift is found with added rotation. The pitching angle amplitude

of 35°–45° was found to be optimum, with a phase angle of 90° between pitch

and plunge (using 2-D solver). This was found by multi-objective optimization.

Wings with corrugated leading edges sometimes produce a higher lift as in the

case of dragonflies.

• The pitching axis nearer to the centre of the wing in the chordwise direction

exploits the vortices shed from both the leading and trailing edges [6]. They

observed that lift and drag increased with an increase in flapping frequency, stroke

amplitude and the advanced wing rotation.

• The unsteady flapping aerodynamics results in the enhanced lift due to the

following mechanisms as described in Chap. 2 and listed below:

– Clap and Fling.

– Rapid pitch up rotation (analogous to Magnus Effect during the stroke

reversals).

– Wake capture (Wing-Wake Reaction).

– Delayed Stall of Leading Edge Vortices.

– Tip Vortex.

– Passive Pitching Mechanism, i.e. the wing torsional flexibility causing pitching

motion.

Summary

Aeroelasticity involves the structural damping and mass characteristics of the flier

object besides the external aerodynamic loads and their dynamic nature. A proper

prediction of these loads and the vibration characteristics help in the optimization

of both the MAV body as well as the flapping wings. The model should prefer-

ably include details of the interacting aerodynamic forces and the way they vary.

These models can be helpful in predicting the flutter margin and any other problems

involving the initiation of the stall.

The aeroelastic phenomena in general are found to be beneficial for the design

of insect mimicking MAVs. To the extent possible, the natural materials for the

membrane and the resilin, supporting the wing at the fulcrum, can be used in their

design. Resilin is reported to be highly elastic. There is a need to do further studies

on the insects like T. javanica, C. purpureous and Cicada where considerable exper-

imental data exists. If it is not feasible to use the natural materials for the MAVs, then

the experimental studies are to be done on the MAV configurations with substitute

synthetic materials like Mylar, to study their aeroelastic effects and fatigue resistance

at the low Re numbers [4].